In mobile communication systems, a tower mounted antenna unit is generally used to receive and transmit signals. Because the antenna unit is usually passive, a radio remote unit (RRU) needs to provide a high power transmission signal, and this signal is transmitted by an antenna unit connected to the RRU via a feeder cable.
As shown in FIG. 1, the antenna unit in the prior art includes an antenna dipole array 5, a phase shifter network and power combiner/splitter network 6, a multiplexer and demultiplexer circuit module (BiasTee) 9, a transmission unit 7, and a remote control unit (RCU) 8. The RRU includes a transceiver and a digital processing unit (DPU). The RRU is connected to the antenna unit via a feeder line. During signal reception, a weak electromagnetic wave signal transmitted by a mobile station is received by the antenna dipole array 5; this weak signal is phase-shifted by the phase shifter network, and is combined into a received signal by the power combiner/splitter network; the multiplexer and demultiplexer circuit module 9 transmits the received signal to the RRU through the feeder line; the received signal is processed by the duplexer, low-noise amplifier (LNA) and down-converter of the transceiver on the RRU, and undergoes the analog-to-digital conversion (ADC) and filtering (cascaded integral comb (CIC) decimation filter, half band filter (HBF), and finite impulse response filter (FIR)) by the DPU on the RRU; the received signal is sent to the base band unit (BBU), and then to the base station controller (BSC) through the BBU. During signal emission, the signal of the BBU undergoes the clipping of clipper (crest factor reduction (CFR)) and digital-to-analog conversion (DAC) by the DPU on the RRU; the signal is then processed by the transceiver (frequency conversion), power amplifier (PA), and duplexer on the RRU; the signal is transmitted to the phase shifter network and power combiner/splitter network through the feeder line and the multiplexer and demultiplexer circuit module 9; the signal is split into multiple signals by the power combiner/splitter network; the signals reach the antenna dipole array; the antenna dipole array converts the signals into electromagnetic wave signals, and transmits them to the mobile station.
The phase shifter network is designed in a motor-driven mechanical structure; the multiplexer and demultiplexer circuit module 9 extracts the DC power supply and control signaling needed by the RCU 8 from the feeder line; the RCU 8 controls the transmission unit 7, and enables the phase shifter network to adjust the amplitude and phase of each antenna dipole.
During the implementation of the present invention, the inventor discovers at least the following problems in the prior art:
The phase shifter network adopts a complex mechanical structure and is unreliable in the process of adjusting the amplitudes and phases of the antenna dipoles.